1. Technical Field
This invention relates to a solid lubricant supply system, an image forming apparatus, and a process cartridge.
2. Related Art
An image forming apparatus, such as a printer, a facsimile machine, a copier, etc., with a solid lubricant supply system that supplies solid lubricant to a surface of an image bearer, such as a photoconductor, an intermediate transfer belt, etc., to either protect or minimize a friction on the image bearer is known.
Since a protecting function of the solid lubricant does not work and the image bearer may wear out or deteriorate if images continue to be formed after the solid lubricant runs out, the image forming apparatus typically has a residual solid lubricant quantity detecting unit to monitor the amount of lubricant remaining.
FIG. 16 is a schematic perspective view of a conventional solid lubricant supply system that includes a residual solid lubricant quantity-detecting unit. Specifically, as shown there, the conventional solid lubricant supply system is configured by a solid lubricant holding unit 143 made of conductive member and a solid lubricant 140. The conventional solid lubricant supply system also includes a first fixed electrode 181 that contacts one end of the solid lubricant holding unit 143 when the residual quantity of solid lubricant declines to a given level. The solid lubricant supply system also includes a second fixed electrode 182 that engages with the other end of the solid lubricant holding unit 143 when the residual quantity of solid lubricant declines to a given level as well. A detecting circuit 183 is connected to the first and second fixed electrodes 181 and 182 that supplies a given voltage between the first and second electrodes and detects whether or not a current flows therebetween. The solid lubricant-holding unit 143 is biased toward a solid lubricant supplying unit, not shown, by a pair of springs 142.
At the early stage of usage of the solid lubricant, the solid lubricant holding unit 143 is separated from these electrodes and no current flows therebetween. When the solid lubricant is gradually scraped off by sliding friction of the solid lubricant supplying unit, the solid lubricant holding unit 143 moves toward the solid lubricant-supplying unit due to biasing force of the pair of spring 142. When the quantity of the solid lubricant 140 becomes less than a given level, the conductive solid lubricant holding unit 143 engages both the first and second fixed electrodes 181 and 182 and a current flows between these first and second electrodes, the detecting circuit 183 determines that the quantity of the solid lubricant is less than the given level. When it is determined that the quantity of solid lubricant is less than the given level by the detecting circuit 183, a message to the effect that the solid lubricant has run out and needs to be replaced with a new solid lubricant is displayed by a displaying circuit 184 on the image forming apparatus.
After the conductive solid lubricant holding unit 143 engages both the first and second fixed electrodes 181 and 182, and accordingly the detecting circuit 183 determines that the quantity of solid lubricant is less than the given level, the solid lubricant holding unit 143 is inhibited to move any more toward the solid lubricant supplying unit due to interference of the first and second fixed electrodes. Therefore, after the above-described determination of the detecting circuit 183, the solid lubricant held by the solid lubricant holding unit 143 is neither moved nor shaved by the solid lubricant supplying unit. In other words, after the determination of less than the given level of a residual quantity of the solid lubricant, the solid lubricant is not consumed any more.
Because errors occur in assembling these first and second fixed electrodes 181 and 182, it is difficult for the above-described conventional residual solid lubricant quantity detecting unit to detect when the solid lubricant is about to run out (herein also referred to as a terminal stage). Accordingly, the conventional gauges are generally designed to detect a stage earlier than the terminal stage (herein also referred to as a near end stage) at which the solid lubricant is not completely spent. Accordingly, when the residual solid lubricant quantity-detecting unit detects the residual quantity of the solid lubricant at the terminal stage, the solid lubricant is not completely spent. Consequently, the lubricant is partially wasted when replaced at this stage. At the same time, the images are sometimes continue to be formed even after the near end stage is detected but before the solid lubricant is subsequently replaced with a new solid lubricant, in which case the photoconductor may be damaged due to insufficient lubrication.